1. Field of the Invention
This invention relates generally to the use of optical devices to sense the progress of processes, transmit signals related to such progress, detect such signals and extract from such signals information to control such processes. More particularly, this invention relates to the removal of interferences from optical emission signals during endpoint determination in dry etching processes for the fabrication of micro-electronic devices, including, but not limited semiconductor devices, and for other micro-machining processes, which are accompanied by the emission of light from the reactants, products, film being etched or some combination thereof.